614 research outputs found
Control of Regime of Unified Interphase Power Controller by the Use of Rotary Transformer
Interphase Power Controller (IPC) has some properties of the source of the current. The use of these technical devices in electrical networks, in addition to optimization of the flow distribution, contributes to limiting of short-circuit currents and limits the level of distribution of electromechanical transients between energy systems. The increase of IPC controllability allows assigning some control function upon them and ensuring a more favorable operation of the energy system generators. We have studied a variant of such a device, which is controlled by a rotary phase-shifting transformer using the asynchronous electric machines with locked phase-wound rotor
CHARACTERISTIC OF STEADY-STATE REGIME FOR ONE OF SCENARIOUS OF MOLDOVA RIGHT BANK POWER SYSTEM INTEGRATION TO ENTSO-E
The article deals with the integration scenario of Moldavian power system to ENTSO-E. Various options of the development of power generation on the territory of the Republic of Moldova have been proposed and analyzed in order to correspond with Energy Strategy of the Republic of Moldova until 2030. Analysis of steady-state operation has been performed regarding active power losses for entire power system, and also for the each element with differentiation on voltage levels. The computation and estimation of static stability factor for active power and for voltage were performed. Import/export of energy was estimated, and other indices of regime of energy system were analyzed as well. Technically effective variants were selected as a result of comparative analysis
The Use of Chokes to Improve the Quality of the Static Frequency Converter
The aim of the work is to develop technical measures to improve the quality of the power transmission process through electrical link, which contains a frequency converter based on a PST (phase-shifting transformer) with circular rotation of the output voltage phase in relation to the input, made according to the triangle scheme and controlled by means of power electronics. To achieve this goal, the use of longitudinal inductive elements (chokes) has been proposed as one of the measures that significantly improves the controlled mode parameters in the process of frequency conversion. The problem has been solved by performing computational experiments on simulation models of electrical links, combining two power systems with a frequency of 60 and 50 Hz, respectively. The structure of electrical links at various stages of the study has included several circuit variants of a frequency converter (single-channel circuit, dual-channel with reversing control winding sections, dual-channel circuit without reversing control winding sections) and has developed by authors earlier. In the process of research, the value of inductance of chokes has been changed, as well as their place of connection. The controlled transmission's characteristics have been analyzed as well. The novelty of the work lies in the use of longitudinally included inductive elements as a possible solution to the problem of improving the quality of power transmission when combining power systems with different operating frequencies using static frequency converters. The optimal values of the parameters of inductive elements, comprised between 0.03-0.035Hn for all circuit versions of the converter, have been identified
SIMULATION OF CHARACTERISTICS OF DUAL-CORE PHASE SHIFTING TRANSFORMER
The role and importance of phase shifting transformers are increased as a result of the further development of integrated power systems. This gives the rise to new technical solutions which entails the necessity of comparison of new developments with existing. The article consider the technical characteristics of dual-core phase shifting transformer which later will be used as a basis for comparison with other competing options and assess of their technical efficiency
Three-Phase Phase-Shifting Transformer with Regulation in Neutral Point
The paper aimed to research mode characteristics of phase shift installation based on one three-phase transformer having three windings. Usually, such installations are two cores: exciting transformer and regulation transformer. In paper the installation functional scheme description, as well main relations which determine currents and voltages character in scheme elements during regulation process are given. It is shown, that installation is able to provide phase shift angle regulation up to . The installation scheme is designed to place the control module in the neutral connection point of regulation windings. Such solution allowing essential reduction of installation rated capacity compare to traditional one and excluding necessity of special isolation of shell. Proposed solution ensure in such mode compact construction and commodity for transportation, mounting and service
Anomalous Dynamic Scaling in Locally-Conserved Coarsening of Fractal Clusters
We report two-dimensional phase-field simulations of locally-conserved
coarsening dynamics of random fractal clusters with fractal dimension D=1.7 and
1.5. The correlation function, cluster perimeter and solute mass are measured
as functions of time. Analyzing the correlation function dynamics, we identify
two different time-dependent length scales that exhibit power laws in time. The
exponents of these power laws are independent of D, one of them is apparently
the classic exponent 1/3. The solute mass versus time exhibits dynamic scaling
with a D-dependent exponent, in agreement with a simple scaling theory.Comment: 5 pages, 4 figure
Scaling anomalies in the coarsening dynamics of fractal viscous fingering patterns
We analyze a recent experiment of Sharon \textit{et al.} (2003) on the
coarsening, due to surface tension, of fractal viscous fingering patterns
(FVFPs) grown in a radial Hele-Shaw cell. We argue that an unforced Hele-Shaw
model, a natural model for that experiment, belongs to the same universality
class as model B of phase ordering. Two series of numerical simulations with
model B are performed, with the FVFPs grown in the experiment, and with
Diffusion Limited Aggregates, as the initial conditions. We observed
Lifshitz-Slyozov scaling at intermediate distances and very slow
convergence to this scaling at small distances. Dynamic scale invariance breaks
down at large distances.Comment: 4 pages, 4 eps figures; to appear in Phys. Rev.
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
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